To many, 7200rpm SCSI drives are becoming more and more passé. The high-end market, for example, is gearing up for a move to an incredible 15k rpm operation. "Enterprise-class" workhorses will similarly follow suite, eventually moving to 10k rpm spindle speeds. This leaves the poor 7200rpm class as something that will eventually be relegated "only" to ATA drives. But not quite yet...
7200rpm drives have reached a venerable sixth-generation level of refinement. Quantum was first out the door with the Atlas V, an impressive follow up to the Atlas IV, StorageReview.com's 1999 Editor's Choice for a 7200rpm SCSI drive. It's Seagate's Barracuda 18XL, however, that's most intriguing.
The 18XL is a product of transition. Instead of taking the Barracuda series to the next level of capacity (a 36 gig, low-profile product such as the Atlas V), Seagate has chosen to sit back and implement features that will prepare the Barracuda line for a transition to 10k rpm speeds. The 18XL features the same platters found in the Cheetah 18XL/36LP, namely the smaller 3" kind. Up to this point, such smaller platters were found only in 10k rpm units, a side effect of the desire to shave seek times to a bare minimum while also controlling the heat and noise generated by such units.
The flagship Barracuda 18XL features three of these smaller platters, each holding 6.1 gigs of data, yielding a net capacity negligibly larger than the older 'Cuda 18LP. The lack of increased capacity does have its benefits, however. Smaller platters combined with a lower platter count (three for the 18XL vs. the six found in the 18LP) result in a unit that should be in theory much quieter and cooler-running due to reduced spindle motor requirements. Of more interest to many, however, is the resulting seek times. Thanks largely due to the reduced-diameter media, the 18XL sports a specified seek time of just 5.8 milliseconds, the first 7200rpm drive to plumb the sub-six depths. Seagate has also updated the unit's buffer size to a contemporary 2 megs.
Interestingly, Seagate's marketing department seems to have already made a switch, trumpeting 15k drives as the high-end and 10k rpm drives as "mainstream," knocking the poor Barracuda 18XL all the way down the SCSI totem pole to "entry-level" status... a place formerly inhabited only by the dubious Medalist Pro SCSI . Make no mistake, however, the 18XL is an enterprise-class drive, as evidenced by its 1.2 million hour MTBF figure and a five-year warranty. Alright, we can already envision many folks sneering at the MTBF reference but surely the five-year warranty is worth something in an age where other "entry-level" warranties have fallen to 3 years for SCSI disks and 1 year for ATA drives!
The Barracuda 18XL is the first drive to receive an individual review following the rollout of our new testbed. As a result, we're providing figures collected on both the new and old systems. We'll continue to do so for an interim period before phasing out the old testbed entirely.
WB99/Win2k Low-Level Measurements